It has been known heretofore that carbon monoxide in the exhaust from an internal combustion engine can be converted to harmless carbon dioxide by causing it to flow over an electrically heated coil. However, this has little or no beneficial effect on other noxious components which may be present in the exhaust, such as oxides of nitrogen, sulfur and lead.
Electrostatic precipitators have been used for removing undesired impurities in the air or in various gases. For example, U.S. Pat. No. 3,558,286 shows such a precipitator for removing impurities present in the exhaust from an internal combustion engine on a vehicle.